Among all the approaches and measures that have been presented in the past years as concrete solutions for deterring counterfeiting and prevent unlawful and fraudulent wins within casinos, RFID-based solutions have received the greatest attention from both the industry and research communities.
Radio Frequency Identification technology is currently widely used in multiple industry sectors including manufacturing, transportation, postal tracking, medical, pharmaceutical and highway toll management. A typical RFID system configuration comprises an RFID transponder usually located on the object to be identified, an RFID interrogator or reader and a computing device. The interrogator is typically made of a radio frequency module, a control unit and a coupling element that transfers a sufficient amount of energy to the transponder. The transponder actually carries the data and it normally consists of a coupling element and an electronic microchip.
Several patents pertaining to RFID-based casino gaming chip monitoring for anti-counterfeiting purposes and player tracking have been issued. U.S. Pat. No. 5,166,502 (Rendelman et al.) shows a construction of radio frequency transponder embedded in a gaming chip. The transponder is tagged with information concerning the chip such as chip identity and value. The particular transponder described in that patent was specifically designed to work with slot machines. However, extending the application field of aforementioned chip to gaming tables such as black jack tables or baccarat was not considered in this patent, and it would not work because the information contained in the chip cannot be changed.
In U.S. Pat. Nos. 5,651,548 and 5,735,742, French et al. presents other RFID-based apparatus and methods of tracking gaming chip movement within casinos. These methods address the flaws of the previous patent by allowing chip tracking at various places within the casino including gaming tables and chip trays. Possibility of reading and writing in the integrated circuit containing token information is also explored. However, the solution proposed in French et al. is difficult to implement because an RF antenna configured the way it is described in the patent, would radiate on adjacent betting positions. This means that while interrogating chips lying on a given position, chips located on adjacent betting position will respond as well. French et al. does not disclose any method to control the radiating behaviour of the antenna. FIG. 1 (a, b, c, d, e and f), identified as Prior Art, illustrates the radiation pattern of center driven dipole antennas of various lengths (operating at 14 MHz) of the type that may be considered for use under a gaming table because of their simple construction. The plot shows the E field (radiated) for antennas whose length are ¼, ⅜, ½ and 1⅛ times the wavelength. For shorter antenna, the beam width is quite wide and approaches 90 degrees. With decreasing antenna size, the beam also decreases but this also introduces side lobes as can be seen on FIG. 1 (d and f) This means that for reasonable sized antenna structures that could be placed under a gaming table; the “illuminated” area is quite large and not compatible with the sizes and spatial discrimination needed for chip localization on the surfaces of gaming tables. Increasing the operating frequency could be though as a possible solution since this would apparently decrease the wavelength and thus decrease the dipole length. However, radio spectrum usage allocations charts restrict the use of various frequency bands e.g., ISM bands within defined power limits.
Further, French et al. does not address the issue of malicious players which could try to defeat the system by bringing strong interference sources in the close vicinity of the system. The use of shielding layers made out of appropriate material in this patent efficiently solves this problem.